Binderless cast photoflash compositions

ABSTRACT

A BINDERLESS CAST PHOTOFLASH COMPOSITION CONSISTING OF ABOUT 40% BY WEIGHT METAL POWDER DISPERSED IN ABOUT 60% BY WEIGHT MOLTEN INORGANIC OXIDIZER. THIS COMPOSITION IS LESS SENSITIVE TO IMPACT, FRICTION, AND STATIC ELECTRICITY THAN FLASH POWDERS CONSISTING OF FINELY DIVIDED LOOSE-POWDER METAL AND OXIDIZER MIXTURES.

United States Patent ABSTRACT OF THE DISCLOSURE A binderless cast photofiash composition consisting of about 40% by weight metal powder dispersed in about 60% by weight molten inorganic oxidizer. This composition is less sensitive to impact, friction, and static electricity than flash powders consisting of finely divided loose-powder metal and oxidizer mixtures.

GOVERNMENT INTEREST The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.

BACKGROUND 'OF THE INVENTION This invention relates to a binderless cast photofiash composition consisting of a low-melting inorganic oxidizer and a powdered metal.

Photoflash cartridges and bombs used in night aerial reconnaissance photography contain a loose-powder pyrotechnic charge which is a metal and an oxidizer in a finely divided condition. These photofiash powders are hazardous in any quantity in that they are highly sensitive to impact, friction, and static electricity. The processing and the manufacture of cartridges or bombs is one of the most hazardous in pyrotechnics. The problems encountered in the creation of a fire ball from a flash charge, its development, duration, size, shape, useful light output, etc., depend on many factors and are even more complex than the problems of ordinary pyrotechnic flames. The present invention provides a photofiash composition which is comparatively safe to manufacture and handle.

DESCRIPTION OF THE INVENTION In accordance with the present invention a photofiash composition was prepared by adding metal powder to melted oxidizer in suitable heated mixing equipment and then pouring the mixture into a charge case. Alternatively, a mixture of coarse oxidizer and metal powder can be heated until the oxidizer melts, the mixture stirred, and then poured into the charge case. The mixture can be loaded into the casing, then heated until the oxidizer melts and the entire mass compacted by vibration. A typical photofiash composition in accordance with this invention contains about 40% by weight metal powder and about 60% molten oxidizer. The preferred metal is aluminum. The preferred oxidizer includes a mixture of salts selected from the group consisting of potassium perchlorate, lithium perchlorate, ammonium perchlorate, sodium perchlorate, and calcium perchlorate. The metal to oxidizer weight ratio ranges from 40:60 to 60:40.

The following examples will better illustrate this invention.

Example I 60% by weight of a prefused eutectic mixture comprising a blend of 68.6% lithium perchlorate and 31.4% sodium perchlorate was melted in an open crucible by heat- 3,726,728 Patented Apr. 10, 1973 ing to about 207" C. The melt was maintained at about 230-250 C. while 40% by weight powdered aluminum (20a) was added while mixing with a spatula. The resultant slurry was cast into small test cartridges containing 120-130 grams. The cartridges were steel cases 1%" x 3%" having a Teflon mandrel positioned in the center. The slurry was cast around the mandrel and permitted to cool at room temperature thereby forming a solid. The mandrel was removed and the well formed was later filled with a high explosive to trigger the photoflash composition. Two explosives were used; one, an extruded explosive containing HMX with 15% Viton-Teflon binder, and the other was tetryl in the form of pressed pellets.

The average peak candlepower of 32 cartridges containing this cast binderless composition which were made and tested over a period of one year was 33.4 x 10.

Example II 50% by weight of the same eutectic mixture, lithium/ sodium perchlorate and 50% by weight powdered aluminum were prepared as described in Example I. Six cartridges containing this composition were tested and averaged a peak candlepower of 502x10 The 50:50 metal to oxidizer ratio is much thicker than the 40:60 ratio described in Example 'I, but still can be cast by pouring and the peak candlepower is increased.

Example III Example I was repeated several times substituting for the LiCl -NaClO eutectic mixture the following blends of perchlorates and maintaining the molten mixture 20- 30 C. above the indicated melting temperature: 57% LiClO -21.6% NaClO 21.4% Ca(ClO (202 C.); 66% LiClO 34% NI-LCIO, (182 C.); 70.8% LiClO 29.2% KClO, (207 C.). These compositions were cast and tested as in Example I. The light output of each compared favorably with the lithium/sodium perchlorate-aluminum photofiash composition set out hereinabove.

M123-size flash charges containing 40%, 45%, 50% and 55% aluminum powder (20 micron) and the lithium perchlorate-sodium perchlorate eutectic mixture with a one-inch tetryl burster were prepared and tested. Average peak candlepower of these devices was approximately 300 l0 CP (range 240-340X 10 CP) and there was no appreciable change in peak with increasing metal content. Increase in metal content resulted in a higher integral light output, however. This increase in integral (or total) light was small over the first 10 milliseconds, but became greater over 40 milliseconds.

The perchlorate oxidizers used herein are comparatively safe to handle and give excellent light output. The casing may be of the usual steel, glass tape, plastic or other suitable material so long as the atmospheric moisture is kept away from the cast composition and the casing material is compatible with the composition.

What is claimed is:

1. A photofiash composition having a continuous solid phase and a dispersed solid phase; said continuous phase comprising from 40 to 60% by weight of a mixture of oxidizers selected from the group consisting of potassium perchlorate, lithium perchlorate, sodium perchlorate, ammonium perchlorate and calcium perchlorate; and said dispersed phase comprising from 40 to 60% by weight finely divided particulate aluminum; said composition producing a flash having a peak candlepower in the range of from about 33.4)(10 to about 340x10 when activated.

2. The composition according to claim 1 in which the References Cited continuous phase approximates a eutectic mixture. UN TED TATES PATENTS 3. The composition according to claim 1 in which the I S continuous phase is a eutectic mixture consisting essen- 3106497 10/1963 Weil "1 1 17 3,293,187 12/1966 Markowitz 149-40 X tially of lithium perchlorate and sodium perchlorate. 5 I

3,331,203 7/1967 Kaufman et al. -149-17 X 4. A composition according to claim 1 in which the 3 522 334 7 0 continuous phase is a eutectic mixture consisting essen- 197 Hunter et 149 17 X tially of lithium perchlorate and ammonium perchlorate. I I

5. A composition according to claim 1 in which the CARL QUARFORTH Primary Exammer continuous phase is a eutectic mixture consisting essen- 10 NELSON, Assistant Examiner tially of lithium perchlorate and potassium perchlorate. U S 1 6. A composition according to claim 1 in which the C ratio of oxidizer to aluminum is about equal. 14940, 76, 77, 113; 43193 

